The present invention relates to a semiconductor device and a manufacturing method thereof wherein a semiconductor element is mounted on a film-shaped substrate having flexibility.
A semiconductor element is mounted on a film substrate which is a film-shaped substrate used in cellular phones and digital cameras, and is molded with a resin. As a method of mounting the semiconductor element on the film substrate, TAB (Tape Automated Bonding) method is known. In the TAB method, a hole for mounting an element is formed in the film substrate, and by laminating metal foil to a surface of the film substrate and etching the metal foil, a plurality of finger leads which project inside the hole are formed. Bump electrodes of the semiconductor element are welded to these finger leads, and the semiconductor element is thereby mounted on the film substrate.
A conventional semiconductor device having the configuration as mentioned above has a problem that, when the bump electrodes of the semiconductor element are welded to the finger leads of the film substrate, the finger lead contacts a corner of the semiconductor element to be scratched or to be potentially short-circuited. To solve such a problem, some semiconductor devices are provided with an insulating film. FIG. 20 is a cross-sectional view of a semiconductor device disclosed in Official Gazette of Japanese Unexamined Patent Publication Hei 10-340923. The semiconductor device shown in FIG. 20 represents a state where a semiconductor element 101 is mounted on a film substrate 103 by the TAB method. In this semiconductor device, bump electrodes 105 of the semiconductor element 101 are fixed to finger leads 104 which project inside a hole 100 formed in the film substrate 103 by thermocompression bonding. An insulating film 102 formed on the bump-electrode side of the semiconductor element 101 is made by applying an insulating resin to a semiconductor wafer to form the semiconductor element 101 by spin coating and drying the applied resin. Since the bump electrodes 105 formed on the semiconductor wafer are covered with the insulating film 102 at this time, the whole surface of the insulating film 102 is half-etched. Consequently, the insulating film 102 is removed to the intermediate of the film thickness, so that the bump electrodes 105 project upward from the insulating film 102. The insulating film 102 at this time is set to have a thickness of 80% to 90% of the height of the bump electrodes. In the semiconductor wafer on which the insulating film 102 is formed as mentioned above, a groove for cutting is formed by etching. The semiconductor wafer is cut along this groove, and individual semiconductor elements 101 are thereby produced.
Since the insulating film 102 is formed on the bump-electrode side of the semiconductor element 101 as mentioned above, the situation is prevented wherein, when the finger leads 104 are welded to the bump electrode 105, the finger lead 104 directly contacts an edge part of the semiconductor element 101 and a short circuit thereby occurs. After the semiconductor element 101 is mounted on the film substrate 103 as mentioned above, the junctions of the bump electrodes 105 and the finger leads 104 are molded with a resin 106.
In the conventional semiconductor device shown in FIG. 20, the hole 100 for mounting the semiconductor element 101 is formed in the film substrate 103, and molding is done by filling this hole 100 with the resin 106. However, in some recent semiconductor devices, the hole 100 for mounting the semiconductor element 101 is not formed in the film substrate 103, but the configuration is employed wherein the bump electrodes 105 of the semiconductor element 101 are directly connected to the electrodes formed on the film substrate. In a semiconductor device having the configuration as mentioned above, the bump electrodes 105 of the semiconductor element 101 are placed on the electrodes formed on the film substrate, and the electrodes and the bump electrodes 105 are connected by thermocompression bonding. The semiconductor device is manufactured by filling the space between the semiconductor element 101 and the film substrate 103 configured as mentioned above with the resin.
When a semiconductor device is manufactured by filling the space between the semiconductor element 101 and the film substrate 103 with the resin, the space between the semiconductor element and the film substrate has to be completely filled with the molding resin so that the resin may not include a cavity, an air bubble or the like. A cavity, an air bubble or the like inside the resin, if any, becomes a cause of corrosion, breakage, disconnection and so on when the semiconductor device is used for a long time.
However, in the conventional semiconductor device, when the insulating film is formed between the semiconductor element 101 and the film substrate 103 for the purpose of the prevention of, for example, the short circuit which occurs when the semiconductor element 101 is mounted thereon, there is only a little space between the insulating film 102 of the semiconductor element 101 and the film substrate 103, and it is difficult to fill the space completely with the resin with no air bubble included in the space. Especially, as a pitch between electrodes becomes smaller and a space to be filled becomes narrower, the possibility that a cavity or an air bubble may be produced within the resin may be increased in the case where such a space is filled with the resin.